Been Using 91 instead of 93
 

I've never had a car that needed premium fuel. The gas stations in my area have 91 marked as a premium fuel. I was reading the manual today and it says that I should be putting in 93!

I've already put 4000 miles on the car with 91 exclusively.

What kind of damage could result from having done this for so long?

None. The only thing available in CA is 91.....so you're good.

your floorboards are gonna overboost. You would need to bring it to a mechanic and check your intake welds for damage.






















you could also read a few more sentences of your owners manual after the 93 octane bit.....

I dont think 91 fuel will result in any damage to ur car, but Im sure that it damaged ur heart already.

91 octane in the BRZ/FR-S?


It's totalled, bro.

Yikes, this whole time i thought the floorboards were supposed to boost that way! Little did I know that it's from the wrong fuel!!!

There's so much information littered across this manual, that depending on what page you start from you get a different message.

Pg 423
"If you use gasohol in your SUBARU, be sure that it has an octane rating
no lower than 93 AKI."

Pg 421
"Using a gasoline with a lower octane rating can cause persistent and heavy
knocking, which can damage the engine."

But in anycase, I found the one sentence you are referring to that says

Pg 421
"If 93 AKI (98 RON) fuel is not readily available in your area,
unleaded gasoline with an octane rating of 91 AKI (95 RON) may be
used with no detriment to engine durability or driveability."

Those statements are in direct opposition to one another but I'll be sure to point to that one should anything bad happen.

three things to keep in mind

1. Pg 421 refers to the general notion that putting lower octane gas into any car designed for high octane is bad. The key word here is "can" and in real world means if you put 87 or something then you will most likely get pinging under load. This is a catch all warning, it is simply the physics of the process.

2. Modern engines have their fuel/spark electroncially controlled. The car will adjsut to lower octane. You'll lose a few horsepower and the car may ride a little rougher.. but..

3. in the case of 91 vs 93, the difference is arguably minimal, furthermore one has to keep in mind whether the 93 is true or just a 91 with ethanol additive. I put shell 91 into my car and have had no problems.

the whole ethanol vs gas is a seperate discussion.

FILL AWAY AND DON'T FRAY (or whatever)

Usually

91 = "premium"

93 = "super"

:bellyroll:

In VA it's a little wonkier than that.

87 = regular
89 = premium
91/93 = super

I alternate between Shell 91 (0% ethanol) and Petro 94 (up to 10% ethanol) and don't notice much difference most of the time. I do notice a bit of knock on throttle tip in on REALLY hot days at very low rpm's on Shell 91, but nothing up top and it's a very brief knock.

I haven't even bothered to see if 93 is available where I live. I've only seen 91 and approaching 13K miles I couldn't be happier.

No worries, today I witnessed an FRS owner putting 87 gas into their tank. Poor car

:popcorn:None.

The only damaged you did was damage to your wallet since you saved more money and it was thicker, thus stretching it.